Abstract : This paper presents three-dimensional numerical simulations of non-colloidal dense sus-pensions in a wall-bounded shear flow at zero Reynolds number. Simulations rely on a fictitious domain method with a detailed modelling of particle-particle and wall-particle lubrication forces, as well as contact forces including particle roughness and friction. This study emphasizes the effect of walls on the structure, velocity and rheology of a moderately confined suspension channel gap to particle radius ratio of 20 for a volume fraction range 0.1 ≤ φ ≤ 0.5. The wall region shows particle layers with an hexagonal structure. The size of this layered zone depends on volume fraction and is only weakly affected by friction. This structure implies a wall slip which is in good accordance with empirical models. Simulations show that this wall slip can be mitigated by reducing particle roughness. For φ 0.4, wall-induced layering has a moderate impact on viscosity and second normal stress difference N 2. Conversely, it significantly alters the first normal stress difference N 1 and can result in positive N 1 , in better agreement with some experiments. Friction enhances this effect, which is shown to be due to a substantial decrease in the contact normal stress |Σ c xx | where x is the velocity direction because of particle layering in the wall region.